Origin and evolution of the granite/serpentinite reaction zones at Wiry, Lower Silesia

Abstract

Contact schists between Variscan hybridal granitoid apophyses and older serpentinite at Wiry, Lower Silesia, are composed of phiogopite and chlorite, and their alteration products (vermiculite, smectite, regularly interstratified mica/vermiculite, various interstratified chlorite/vermiculite and chlorite/smectite with asymmetric iron location, and three-component interstratified mica/vermiculite/chlorite), as recognized by means of XRD examination and computer simulations. The peak contact metamorphism yielded disseminated tremolite-to-pargasite amphiboles, and minor apatite. Its conditions, determined from aluminium content and fluid inclusions in hornblende, achieved 2.6 Kbar and 560°C. The parent solutions had Ca-Na-CI composition of variable calcium and sodium proportions; the variations were related to albitization of the adjacent Strzegom granitoids. The layer silicates assemblage may be considered as an equivalent of a predecessor of weathering silicate nikiel ores from the worldwide-known deposit at the neighboring ultrabasic massif of SzkIary.